Current techniques for positioning medical treatment devices (e.g., magnets for Transcranial Magnetic Stimulation (TMS) studies) typically are simple manual methods or complex robotic approaches designed for research. The manual approaches are very accurate and the complex approaches require expensive and complex imaging or computational systems to determine three dimensional spatial coordinates for positioning reference. Both approaches have severe clinical limitations. The manual methods do not provide a convenient means for repeated and accurate placement, while the three dimensional spatial methods based on imaging modalities are expensive, time consuming, and not conducive to clinical use. A positioning technique for clinical use is desired that provides a simple way for the operator to freely move and place devices, like a TMS magnet, in a time-efficient and inexpensive manner.
In accordance with the conventional manual placement technique, a treatment position on the patient's head or a position used to find a treatment position (i.e., the patient's motor threshold position (MTP)) is determined by a user moving by hand a treatment device near a predicted treatment area. More details of techniques for determining the MTP are also described in related U.S. patent application Ser. No. 10/714,741, filed Nov. 17, 2003, the contents of which are incorporated herein by reference.
The shortcomings of such manual methods is that movement of the device is constrained, making it difficult to determine the proper treatment location. Also, even once the proper location of the treatment area is located, maintaining the device at the proper location is cumbersome. For example, the problem of applying marks to the patient has been addressed in the art by applying a swim cap or similar conformal headgear to the patient and marking the headgear rather than the patient. Of course, this approach requires careful registration of the headgear during subsequent therapy sessions, which is crude, imprecise, and highly operator dependent. Moreover, such an approach still requires accurate coil placement and a mechanism for holding the coil in place.
On the other hand, the Brainsight™ System developed by Rogue Research, Inc. of Montreal, Canada and distributed by Magstim is complex and is designed primarily for research purposes. This system uses diagnostic images from MRI to determine the spatial relationship between internal anatomy and external landmarks and then aligns to the external landmark for therapy or other studies requiring accurate localization. While this approach is useful for research purposes, it is highly impractical and complex and is thus not usable in general clinical practice. Moreover, such techniques have generally been used to overlay coordinate systems onto images and not for identifying particular treatment positions for specific therapies.
Also, other complex methods include the use of robotic, machine-controlled arms for positioning the treatment device with respect to the patient and holding the device in place during treatment. While these techniques provide controlled movement and placement of the coil, they are quite expensive and do not provide for repeatable placement of the coil with respect to a particular patient's head in a clinical setting. As a result, the manual and/or complex imaging techniques described above must also be used for placement of the coil with respect to the patient.
Therefore, there is a need cost-effective and intuitive way of accurately and repeatably positioning a treatment device.